Question

我正在使用commmand：

在Ubuntu，python 2中测试一些map reduce代码

 #!/usr/bin/python

import sys

def reducer():
    max = 0
    min = 1
    old_tuple = ('foo', 'bar')
    i = 0

    for line in sys.stdin:
        data = line.strip().split("\t")

        if len(data) != 3:
            continue

        city, year, value = data
        new_tuple = (city, year)

        if old_tuple != new_tuple:
            if i != 0:
                print "{0}\t{1}\t{2}\t{3}".format(old_tuple[0], old_tuple[1], max, min)            
                max = 0
                min = 1
        i += 1    
        old_tuple = new_tuple
        if min > value:
            min = value

        if max < value:
            max = value 


    if old_tuple != ('foo', 'bar'):
         print "{0}\t{1}\t{2}\t{3}".format(old_tuple[0], old_tuple[1], max, min) 



if __name__ == '__main__':
    reducer()

我得到最大但不是min的正确输出，我得到min的值为1，好像它没有从它的原始值改变。每个单独的值'value'都小于1，因此在第一次迭代到for循环min时应该更改为第一个值，然后在进一步迭代时更新min。我是在放松自己的想法还是代码中有一个愚蠢的错误？请帮忙！

Alert   2009    0.215236752 1
Winnipeg    2017    0.032557214 1

我得到的输出看起来像

  import java.util.Scanner;

    public class Coursework {

public static void main(String[] args) {
    final int linesOfMatrix; //number of lines in the matrix

    System.out.println("Enter number of lines: ");

    Scanner sc = new Scanner(System.in);
    linesOfMatrix = sc.nextInt();       
    Scanner sc2 = new Scanner(System.in);

    String [][] matrix = new String [linesOfMatrix][]; // declare the Matrix

    for(int i=0; i < matrix.length; i++) {
        System.out.println("Enter a value for the string " + (i+1) + " 
    through a space");
        matrix[i] = sc2.nextLine().split(" ");
    }
    sc.close();
    sc2.close(); 

            //below must be unique sort, but he dosen't work rigth

    for(int i=0; i < matrix.length; i++){   
        for(int j=0; j < matrix[i].length-1; j++){
            if(matrix[i][j].equals(matrix[i][j+1])){
                matrix[i][j+1] = matrix[i][j+1];
            }


        } 
    }
        System.out.println("Matrix");
        for(int i=0; i < matrix.length; i++){
            for(int j=0; j < matrix[i].length-1; j++){

                System.out.println("[" +(i) + "][" + (j) + "]= " + matrix[i]
    [j] + " [" + (i) + "][" + (j+1) + "]= " + matrix[i][j+1]  );
            }

        }
    }
    }

Answer 1

首先，我使用min和max作为关键字的变量名。更改后

min => minimum 
max => maximum

输出仍然不正确。实际上是同样的问题。只是在尝试以更加Pythonic的方式获得最小值和最大值之后，我才开始工作。我是Python的新手，所以这可能仍然不是最好的Pythonic方式，但下面的代码至少可以根据需要获得最小值和最大值。

#!/usr/bin/python

import sys
import math

def reducer():
    list_ = []
    old_tuple = ('foo', 'bar')
    i = 0

    for line in sys.stdin:
        data = line.strip().split("\t")

        if len(data) != 3:
            continue

        city, year, value = data
        new_tuple = (city, year)

        if old_tuple != new_tuple:
            if i != 0:
                print "{0}\t{1}\t{2}\t{3}".format(old_tuple[0], old_tuple[1], max(list_), min(list_))        
                list_ = []    

        i += 1 
        list_.append(value)   
        old_tuple = new_tuple

    if old_tuple != ('foo', 'bar'):
         print "{0}\t{1}\t{2}\t{3}".format(old_tuple[0], old_tuple[1], max(list_), min(list_)) 


if __name__ == '__main__':
    reducer()

Map Reduce：为什么这段代码给出了最大但不是min的正确输出？

1 个答案: